1. Field of the Invention
The present invention relates to a driving amount controller for controlling a driving amount of a target system (for example, the opening of a throttle valve) by way of the output of a motor.
2. Description of Background Art
The output of an engine in a motorcycle or a four-wheel vehicle is, in general, controlled by use of a throttle grip or an accelerator pedal. More specifically, the output of the engine is determined by regulation according to the turning amount of the throttle grip or the step-in amount of the accelerator pedal.
Ordinarily, a throttle valve is connected to a motor and a return spring, and the regulation of the opening is conducted by a method in which the throttle valve is energized in the valve opening direction by the motor and is energized in the valve closing direction by the motor and the return spring.
Since the opening of the throttle valve is regulated through the motor and the return spring as above-mentioned, a response delay or erroneous deviation may sometimes be generated in the control of the opening of the throttle valve (and in the actual engine output corresponding thereto) in response to the operation of the throttle grip or the accelerator pedal. There have been proposed a variety of devices for coping with such a response delay or erroneous deviation. See, for example, Japanese Patent Laid-open No. 2003-216206, Japanese Patent Laid-open No. Sho 61-106934 and Japanese Patent Laid-open No. 2006-307797.
However, the devices disclosed in Japanese Patent Laid-open No. 2003-216206, Japanese Patent Laid-open No. Sho 61-106934 and Japanese Patent Laid-open No. 2006-307797 have room for improvements as to the response performance and/or erroneous deviation in the control of the opening of a throttle valve.
Regulation of the opening of a throttle valve by a motor involves hysteresis characteristics as shown in FIG. 10. More specifically, where a point determined by the duty ratio DUT [%] of a control signal and the actual throttle valve opening DTH [degrees] is present in a hysteresis region 40 in FIG. 10, the motor 18 does not perform an opening/closing operation. For example, where the throttle valve is present in an initial position (DTH=0), the throttle valve starts operating in the opening direction at the time when the duty ratio DUT of the control signal sent from an electronic control unit (ECU) to the motor is d1 [%]. On the other hand, in the case of causing the throttle vale to operate in the closing direction, the throttle valve returns to its initial position where the duty ratio DUT is d2 [%], which is lower than d1.
Simultaneously, where the throttle valve is held (stopped) in the condition where the actual opening DTH is t1 [degrees], in order to cause the throttle valve to operate in the opening direction, it is necessary for the duty ratio DUT to reach or exceed d3 [%]. On the other hand, in order to cause the throttle valve to operate in the closing direction, it suffices that the duty ratio DUT is at d4, which is lower than d3.
In addition, the main factors which are considered to cause the above-mentioned hysteresis characteristics include a factor intrinsic of the motor, friction in the mechanical system, and energization by the return spring. The factor intrinsic of the motor is the current value at which the motor starts operating, and this current value varies depending on such factors as the position, shape, material and the like of a winding, a core and the like. The friction in the mechanical system includes friction between a motor shaft and a bearing, and friction between a plurality of gears in the motor. The energization by the return spring is the energization of the throttle valve in the closing direction by the return spring connected to the throttle valve.
In addition, the hysteresis characteristics as mentioned above appear when the duty ratio DUT [%] is varied in a constant manner. Other hysteresis characteristics appear when the variation in the duty ratio DUT is being varied.
Japanese Patent Laid-open No. 2003-216206, Japanese Patent Laid-open No. Sho 61-106934 and Japanese Patent Laid-open No. 2006-307797 take no account of the response performance in regulation of the opening of the throttle valve attendant on the hysteresis characteristics as above-mentioned, or of the erroneous deviation between an operation made by the driver and the opening of the throttle valve.